Rotary vane pumps are positive displacement pumps that utilize vanes that work with a cam or sealing surface to draw fluid into and force said fluid out of a pump housing. Although effective, previously developed rotary vane pumps are not without their problems. For instance, previously developed rotary vane pumps are inefficient. One reason for their inefficiency is the utilization of dynamic seals to seal in the fluid being pumped. As a case in point, previously developed rotary vane pumps use a dynamic seal between a rotating input shaft coupled to a rotor and the pump housing in which the rotating input shaft passes through. This dynamic seal results in friction losses and is prone to leakage and failure.
Conventional vanes are also inefficiently designed. Such conventional vane designs result in high shear forces and accompanying friction losses as a relatively large surface area of a side of a vane slides against a wall of the slot in which the vane reciprocates radially inward and outward as an outer edge of the vane slides along the sealing surface of the pump housing. Additionally, previously developed rotary vane pumps which do not use mechanical means to bias the vanes outward to the sealing surface, i.e., which use centrifugal and hydraulic forces to bias the vanes outward, have a vane design or geometry that does not provide adequate hydraulic balancing of the forces exerted upon the vane to drive the vane toward the sealing surface, such that the vane is either overly or under driven outward toward the sealing surface by the hydraulic forces acting upon the vane.
Other problems arise from conventional rotor and drive shaft combinations. For example, the rotor and drive shaft combination of previously developed rotary vane pumps are expensive to manufacture since the rotor and drive shaft are separately machined, and then coupled to one another. In addition, previously developed rotary vane pumps have not been able to be manufactured in miniature sizes for use in low flow situations. As an example, previously developed rotary vane pumps have flow rates which exceed 3 ml per revolution of the rotor and have rotors exceeding 2 inches in diameter. Rotary vane pumps having lower flow rates and rotor diameters have hereto eluded those skilled in the art.
Additionally, previously developed rotor designs have not been able to address the issue of providing rigidity between the dividing members (the material between adjacent slots in which the vanes reciprocate) of the rotor, especially in smaller diameter rotors. Moreover, in prior designs, as the slots are radially oriented, the width of the dividing members steadily decreases as the slots converge toward the center axis of the rotor. Thus, from a top view of the dividing members, they are in the shape of a piece of pie, causing a week point at a base (the pointed end of the “piece of pie”) of the dividing members. The dividing members are thus thin at their bases and have very little material to resist torques applied to the dividing members during use.
Thus, there exists a need for a rotary vane pump that addresses one or more of problems associated with previously developed rotary vane pumps, that is reliable, and inexpensive to manufacture.